Thick film resistor and production method for same

ABSTRACT

An object of the present invention is to provide a thick film resistor excluding a toxic lead component from a conductive component and glass and having characteristics equivalent to or superior to conventional resistors in terms of, in a wide resistance range, resistance values, TCR characteristics, current noise characteristics, withstand voltage characteristics and the like. The present invention is a thick film resistor formed of a fired product of a resistive composition, wherein the thick film resistor contains ruthenium-based conductive particles containing ruthenium dioxide and a glass component being essentially free of a lead component and has a resistance value in the range of 100 Ω/□ to 10 MΩ/□ and a temperature coefficient of resistance within ±100 ppm/° C.

TECHNICAL FIELD

The present invention relates to a thick film resistor essentiallycontaining no lead component and a method for producing the thick filmresistor. The present invention especially relates to thick filmresistors formed in various resistor parts, such as a chip resistor, asemi-fixed resistor, a variable resistor, a focus resistor, and a surgeelement, a thick film circuit, a multilayer circuit board, variousmultilayer composite parts, and the like.

BACKGROUND ART

Generally, a thick film resistor (hereinafter also merely referred to asa resistor) is produced by forming a film composed of a resistivecomposition that contains, as main components, a conductive componentand glass on various insulating substrates and firing this.Specifically, the resistive composition usually in a form of a paste orpaint is printed on an alumina substrate in which electrodes are formedor on a ceramic composite part, and the like to have a predeterminedshape and is then fired at a high temperature of 600° C. to 900° C.Thereafter, a protective coating is formed by an overcoat glass ifnecessary, and then a resistance value is adjusted by laser trimming orthe like if necessary.

The characteristics of the resistor to be required are a smalltemperature coefficient of resistance (TCR), a small current noise,favorable withstand voltage characteristics, favorable process stability(for example, a small change in resistance value by a variation inprocess), and the like.

Conventionally, a resistive composition using, as a conductivecomponent, ruthenium-based oxide powder (hereinafter also referred to asa ruthenium-based resistive composition) has been generally used widely.This ruthenium-based resistive composition can be fired in air, and bychanging the ratio between the conductive component and the glass,resistors having a wide range of resistance value can be easilyobtained.

As the conductive component of the ruthenium-based resistivecomposition, ruthenium dioxide (hereinafter also referred to asruthenium(IV) oxide); ruthenium composite oxides, such as bismuthruthenate, lead ruthenate or the like having a pyrochlore structure,barium ruthenate, calcium ruthenate or the like having a perovskitestructure; or ruthenium precursors such as ruthenium resinate or thelike are used. Especially, in a resistive composition having a highcontent of glass in a high resistance range, the above-mentionedruthenium composite oxides such as bismuth ruthenate or the like arepreferably used rather than ruthenium dioxide. This is because theresistivity of the ruthenium composite oxides is generally higher by anorder of magnitude or more, compared with ruthenium dioxide, and alarger amount of ruthenium composite oxides can be blended compared withruthenium dioxide, and thus, a variation in resistance value is small,current noise characteristics and resistance characteristics such as TCRand the like are favorable, and stable resistors can be easily obtained.

On the other hand, as the glass used as a component configuring thethick film resistor, mainly a glass containing lead oxide is used. Themain reason of this is that the lead oxide-containing glass has a lowsoftening point and has superior characteristics suitable for formingthe thick film resistor, such as having favorable fluidity, wettabilitywith the conductive component, superior adhesiveness to a substrate, anda coefficient of thermal expansion suitable for ceramics, particularlyan alumina substrate.

However, the lead component possesses toxicity and is not desirable fromthe viewpoint of the effect on the human body and pollution. In order todeal with recent environmental problems, electronics products arerequired to comply with the Directive of WEEE (Waste Electrical andElectronic Equipment) and RoHS (Restriction of the Use of the CertainHazardous Substances), and amid this situation, the development of alead-free material is strongly required for the resistive compositions.

Furthermore, the lead component has very good wettability to alumina.Therefore, the lead component is wet and excessively spread over thealumina substrate at the time of firing, and the shape of the finallyobtained resistor becomes an unintended shape in some cases.

Therefore, conventionally, some resistive compositions using, as aconductive component, bismuth ruthenate, alkaline earth metal ruthenate,or the like and using glass containing no lead have been proposed (seePTL (Patent Literature) 1 and PTL 2).

However, a thick film resistor using a lead-free glass and showingsuperior characteristics comparable with a conventional thick filmresistor using lead-containing glass over a wide resistance value rangehas not been obtained yet. Especially, it has been difficult to form aresistor in a high resistance range of 100 kΩ/□ or more. The reason ofthis is considered as follows.

Many of ruthenium composite oxides generally used in a high resistancerange are prone to react with glass to decompose ruthenium dioxidehaving a lower resistivity than the ruthenium composite oxide at thetime of firing the resistive composition at a high temperature.Especially when the ruthenium composite oxide is used in combinationwith glass containing no lead component, it is difficult to suppress thedecomposition to ruthenium dioxide at the time of firing (for example,about 800° C. to 900° C.). Therefore, the resistance value is reduced, adesired high resistance value cannot be obtained, and further, there areproblems of increasing the dependency on film thickness and thedependency on firing temperature.

By using a ruthenium composite oxide powder having a large particle size(for example, an average particle size of 1 μm or more) as described inPTL 1, the above-mentioned decomposition can be suppressed to a certainextent. However, in the case of using such a coarse conductive powder,the current noise and the load characteristics are deteriorated, andfavorable resistance characteristics cannot be obtained.

In order to suppress the decomposition of bismuth ruthenate that is oneof ruthenium composite oxides, using bismuth-based glass as described inPTL 2 in combination is effective. However, the TCR of a resistorobtained by the resistive composition of this combination becomes largein a negative direction in a high resistance range.

A fired film of a resistor was observed with an electron microscope bythe inventors of the present invention, and a sign of forming a network(network structure) in which fine conductive particles are dispersed ina matrix of glass and are in contact with one another are observed.Therefore, it is considered that such a network becomes a conductivepath, and thus, conductivity is shown.

In known resistive compositions using a combination of rutheniumcomposite oxide and lead-free glass, it is extremely difficult to stablyform the above-mentioned network structure (hereinafter also referred toas a conductive network) especially in a high resistance range in whichthe content of conductive particles is small. Therefore, a thick filmresistor containing no lead and being superior in variouscharacteristics such as TCR characteristics, current noisecharacteristics, and variations has not become industrially applicableyet.

CITATION LIST Patent Literatures PTL 1: Japanese Patent Application LaidOpen No. 2005-129806

PTL 2: Japanese Patent Application Laid Open No. H8-253342

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a thick film resistorexcluding a toxic lead component from a conductive component and glassand having characteristics equivalent to or superior to conventionalresistors in terms of, in a wide resistance range, resistance values,TCR characteristics, current noise characteristics, withstand voltagecharacteristics and the like.

Moreover, the present invention is further intended to provide a methodfor producing a thick film resistor, by which variations in resistancevalue, TCR, and the like by firing are small, and thus, a thick filmresistor having stable characteristics in a high resistance range can beobtained.

Solution to Problem

In order to achieve the aforementioned object, the thick film resistorof the present invention comprises a fired product of a resistivecomposition, wherein the thick film resistor contains ruthenium-basedconductive particles that contain ruthenium dioxide and a glasscomponent that is essentially free of a lead component and has aresistance value in the range of 100 Ω/□ to 10 MΩ/□ and a temperaturecoefficient of resistance within ±100 ppm/° C.

In order to achieve the aforementioned object, the method for producinga thick film resistor of the present invention includes:

printing a resistive composition including: a ruthenium-based conductiveparticles that contains ruthenium dioxide, a glass frit that isessentially free of a lead component and is constituted such that in acase where a fired product of a mixture of the glass frit and theruthenium dioxide has a value in a range of 1 kΩ/□ to 1 MΩ/□, the firedproduct exhibits a temperature coefficient of resistance in a plusrange, and an organic vehicle, on an object to be printed; andthereafter

firing the resistive composition at 600° C. to 900° C.

Advantageous Effects of Invention

The thick film resistor of the present invention has a resistance valuein the range of 100 Ω/□ to 10 MΩ/□ and a temperature coefficient ofresistance within ±100 pp m/° C. although lead is not essentiallycontained.

Especially, the thick film resistor of the present invention isextremely useful as a resistor in a medium resistance range to a highresistance range of 1 kΩ/□ or more, particularly a resistor having ahigh resistance range of 100 kΩ/□ or more.

According to the production method of the present invention, theconductive component is not decomposed while firing, and thus, auniform, stable conductive network can be formed in a glass matrix.Accordingly, a thick film resistor having no characteristic degradation,a small process dependency on firing conditions and the like, andmoreover a small variation and superior current noise characteristic ina high resistance range can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a drawing showing an SEM image obtained by analyzing aresistor produced using the resistive composition of the presentinvention by Scanning Electron Microscope/Energy Dispersive X-raySpectrometry (SEM-EDX).

FIG. 1B is a drawing showing a result of mapping the SEM image withrespect to a Ba element.

FIG. 1C is a drawing showing a result of mapping the SEM image withrespect to a Ru element.

DESCRIPTION OF EMBODIMENTS Ruthenium-Based Conductive Particles

The ruthenium-based conductive particles in the present invention arepreferably ruthenium-based conductive particles having 50 percent bymass or more of ruthenium dioxide (RuO₂), more preferablyruthenium-based conductive particles composed of only ruthenium dioxide(RuO₂). Thereby, the resistive composition of the present invention canprovide a thick film resistor in which a stable conductive network ismore easily formed, a variation is small, favorable resistancecharacteristics are obtained also in a high resistance range, and otherelectric characteristics and process stability are favorable, even afterfiring the resistive composition at high temperature, can be obtained.

The ruthenium-based conductive particles may be a mixture or a compositeof ruthenium dioxide and other conductive particles described below.

Note that there is a case where the current noise characteristics areimpaired when different kinds of conductive components are presenttogether in the resistor. Therefore, in the present invention, it ispreferable that the ruthenium-based conductive particles be essentiallycomposed of only ruthenium dioxide.

Especially, it is preferable that the ruthenium-based conductiveparticles in the present invention be essentially free of a leadcomponent and further essentially free of a bismuth component.

In the present invention, “be (or being) essentially composed of only”and “be (or being) essentially free of” allows “contain (or containing)a trace amount” of an unintended impurity, as represented by a casewhere the content of the impurity is 1000 ppm or less, whereas a casewhere the content of the impurity of 100 ppm or less is desired, inparticular.

In the present invention, as the ruthenium-based conductive particles,using ruthenium-based conductive particles having fine particle size isdesired. For example, a value at 50% in mass-based cumulative fractionsof the particle size distribution measured by a laser particle sizedistribution measuring apparatus (hereinafter referred to as the averageparticle size D₅₀) is preferably in the range of 0.01 to 0.2 μm. Byusing such fine ruthenium-based conductive particles, theruthenium-based conductive particles are favorably dispersed in aresistor fired film also in a high resistance range, a uniform andstable fine structure (conductive network) comprising theruthenium-based conductive particles and glass is formed in the film,and a resistor having superior characteristics can be obtained.

When the average particle size D₅₀ of the ruthenium-based conductiveparticles is 0.01 μm or more, the reaction of the ruthenium-basedconductive particles with the glass is easier to be suppressed andstable characteristics are obtained more easily. Furthermore, when theaverage particle size D₅₀ is 0.2 μm or less, current noise and loadcharacteristics are prone to be easier to be improved. Theruthenium-based conductive particles particularly preferably have anaverage particle size D₅₀ of 0.03 to 0.1 μm.

[Glass Frit]

In the present invention, as the glass frit, a glass frit is used, whichis constituted such that when a fired product of a mixture of the glassfrit and the ruthenium dioxide has a value in a range of 1 kΩ/□ to 1MΩ/□, the temperature coefficient of resistance (TCR) of the firedproduct is in a plus range.

The inventors of the present invention found that, in the case of usingthe glass frit having such characteristics, by adjusting the blendingratio between the ruthenium-based conductive particles and the glassfrit to be added, adding an inorganic additives described below, asappropriate, and the like, the TCR can be small in a high resistancerange of 100 kΩ/□ or more. For example, the thick film resistor of thepresent invention can control the TCR within ±100 ppm/° C. in a wideresistance range of 100 Ω/□ to 10 MΩ/□.

The glass frit is preferably such a glass frit that the TCR of the firedproduct of the mixture of the glass frit and the ruthenium dioxide ismore than 0 ppm/° C. and not more than 500 ppm/° C., preferably not morethan 400 ppm/° C., more preferably not more than 300 ppm/° C. when thefired product shows a resistance value of 1 kΩ/□ to 1 MΩ/□.

The glass composition providing a positive TCR in a high resistancerange preferably contains, in terms of oxide, 20 to 45 mol % of BaO, 20to 45 mol % of B₂O₃, and 25 to 55 mol % of SiO₂.

When the content of BaO is 20 mol % or more, the TCR especially in ahigh resistance range can be in a plus range, and when the content ofBaO is 45 mol % or less, the film shape after firing can be easilymaintained in a good state.

When the content of B₂O₃ is 20 mol % or more, a dense fired film can beeasily obtained, and when the content of B₂O₃ is 45 mol % or less, theTCR especially in a high resistance range can be in a plus range.

When the content of SiO₂ is 25 mol % or more, the film shape afterfiring can be easily maintained in a good state, and when the content ofSiO₂ is 55 mol % or less, a dense fired film can be obtained moreeasily.

The glass frit more preferably contains, in terms of oxide, 23 to 42 mol% of BaO, 23 to 42 mol % of B₂O₃, and 35 to 52 mol % of SiO₂.

The glass transition point Tg of the glass frit is preferably in therange of 450° C. to 700° C. When the glass transition point Tg is 450°C. or more, a high resistance can be easily obtained, and when the glasstransition point Tg is 700° C. or less, a dense fired film can beobtained. The Tg is preferably in the range of 580° C. to 680° C.

As to the relationship with the firing temperature at which theresistive composition is fired, the Tg is preferably (the firingtemperature −200)° C. or less, and in this case, the following formula(1) is established.

Tg≦(the firing temperature−200)[° C.]  formula (1)

The average particle size D₅₀ of the glass frit is preferably 5 μm orless. When the D₅₀ is 5 μm or less, the resistance value in a highresistance range is easily adjusted, and when D₅₀ is too small, a voidis prone to be generated in the resistor. The particularly preferablerange of the D₅₀ is 0.5 to 3 μm.

The glass frit may further contain one or more kinds of components suchas metal oxides that can adjust the TCR and other resistancecharacteristics, for example, ZnO, Al₂O₃, Li₂O, Na₂O, K₂O, Nb₂O₅, Ta₂O₅,TiO₂, CuO, MnO₂, and La₂O₃. These components can exert high effects evenin a small amount. For example, these components can be contained in atotal amount of about 0.1 to about 10 mol % in the glass frit, and theamount can be adjusted, as appropriate, according to the intendedcharacteristics.

[Functional Filler]

The resistive composition that forms a thick film resistor of thepresent invention preferably contains, in addition to theabove-mentioned inorganic components, a functional filler (hereinafteralso merely referred to as a filler).

The functional filler in the present invention is preferably compositeparticles obtained by providing glass particles having a low fluidity atthe time of firing, separately from the above-mentioned glass frit, andcausing conductive particles (hereinafter referred to as conductingparticles), prepared separately from the above-mentioned ruthenium-basedconductive particles, to adhere to and be fixed to the surfaces of theglass particles and inside the glass particles in the vicinity of thesurfaces to form a composite. In the present invention, the term “glassfrit” and the term “glass particles” are used distinctively from eachother.

Further, in the present invention, as to the glass componentsconfiguring a thick film resistor, the glass component derived fromglass frit is also referred to as a “first glass component”, and theglass component derived from the glass particles is also referred to asa “second glass component”.

As the glass particles, glass particles having a low fluidity at thetime of firing can be used regardless of their compositions. As anexample, the glass particles are preferably a glass having a glasstransition point Tg′ of 500° C. or more, and especially a glasstransition point Tg′ higher than the above-mentioned glass transitionpoint Tg of the glass frit (i.e., Tg<Tg′ is established). Examples ofthe glass compositions having a high glass transition point Tg′ includezinc borosilicate-based glass, lead borosilicate-based glass, alkalineearth metal borosilicate glasses such as barium borosilicate-based glassand calcium borosilicate-based glass, and the like. However, the presentinvention is not limited thereby.

In the relationship with the firing temperature of the resistivecomposition, Tg′ is preferably (the firing temperature −150°) C. ormore, and in this case, the following formula (2) is established.

Tg′≧(the firing temperature −150)[° C.]  formula (2)

As the conducting particles forming a composite with the glass particlesin the functional filler, metal particles such as silver (Ag), gold(Au), platinum (Pt), palladium (Pd), copper (Cu), nickel (Ni), andaluminum (Al) etc., alloy particles containing these metals, andruthenium-based conducting particles can be used.

Examples of the ruthenium-based conducting particles include, inaddition to ruthenium dioxide, ruthenium composite oxides having apyrochlore structure such as neodymium ruthenate (Nd₂Ru₂O₇) samariumruthenate (Sm₂Ru₂O₇) neodymium calcium ruthenate (NdCaRu₂O₇) samariumstrontium ruthenate (SmSrRu₂O₇), and related oxides thereof; rutheniumcomposite oxides having a perovskite structure such as calcium ruthenate(CaRuO₃), strontium ruthenate (SrRuO₃), and barium ruthenate (BaRuO₃);other ruthenium composite oxides such as cobalt ruthenate (Co₂RuO₄) andstrontium ruthenate (Sr₂RuO₄); and mixtures thereof.

As the conducting particle, one or more kinds of the above-describedexamples can be used, and they may be used as a composite with aprecursor compound such as silver oxide or palladium oxide.

As mentioned above, when different kinds of conductive components arepresent together in a resistor, the current noise characteristics areimpaired in some cases. Therefore, as conducting particles that form acomposite with glass particles in the functional filler, usingruthenium-based conducting particles containing, as a main component,ruthenium dioxide are particularly preferable.

As the conducting particles, using conducting particles having a fineparticle size is desirable, and the average particle size D₅₀ in therange of 0.01 to 0.2 μm is preferable.

In the present invention, a method for producing the functional filleris not limited, and for example, the conducting particles may bedeposited on the surfaces of the glass particles provided in advance bya well-known technique such as a displacement deposition method, anelectroless plating method, or an electrolytic method, to form compositeparticles. In the present invention, the functional filler is desirablyproduced by so-called mechanochemical method in which glass particlesand conducting particles provided in advance are stirred and mixed by aknown stirring means such as a media mill or the like, and the mixtureis subjected to thermal treating (for example, at 850° C. to 900° C.)and thereafter pulverizing, to fix the conducting particles on thesurfaces and/or inside thereof.

According to such a method, composite particles having a dispersestructure in which conducting particles having a small particle size areadhered to/fixed to the surfaces of glass particles having a relativelylarge particle size and inside the glass particles in the vicinity ofthe surfaces can be easily produced.

With the resistive composition used in the present invention, the TCRand the other resistance characteristics can be adjusted easily. Thus,by containing the functional filler, a resistor having a small variationin resistance value and stability in a high resistance range andimproved in characteristics such as withstand voltage characteristics,electrostatic characteristics, and a change in resistance value can beobtained, although a favorable resistor can also be obtained usinginorganic additives described below.

The average particle size D₅₀ of the filler is desirably in the range of0.5 to 5 μm. When the average particle size D₅₀ is 0.5 μm or more, adense fired film is obtained more easily, and when the average particlesize D₅₀ is 5 μm or less, the withstand voltage characteristics are lessprone to be deteriorated. Especially, the average particle size D₅₀ of 1to 3 μm is preferable.

The average particle size D₅₀ of the filler can be controlled byadjusting the pulverizing conditions in the case where the filler isproduced by the above-described mechanochemical method, for example.

The content of the conducting particles contained in the filler ispreferably 20 to 35 percent by mass relative to the filler. When thecontent is 20 percent by mass or more, the resistance value of the thickfilm resistor obtained after firing can be adjusted/controlled easily.When the content is 35 percent by mass or less, good STOLcharacteristics (withstand voltage characteristics) can be obtained.

As shown in Example 1 described below with reference to FIG. 1A to FIG.1C, in the case where glass particles which are essentially free of alead component are contained, and moreover the glass transition point Tgof glass frit is (the firing temperature −200)° C. or less and the glasstransition point Tg′ of the glass particles is (the firing temperature−150)° C. or more, then the glass in the resistor forms a sea-islandstructure. This sea-island structure is a structure in which glass(first glass component) derived from the glass frit forms sea (matrix),and glass (second glass component) derived from the glass particlesforms islands. Such a structure is formed not only in the case ofaddition of the functional filler as a component of a resistivecomposition, but also in the case of using glass particles instead ofthe functional filler. Such a structure is a structure that is not foundin a conventional resistor.

[Other Additives]

In the resistive composition according to the present invention, one ora combination of various inorganic additives generally used for thepurpose of improving and adjusting resistance characteristics such asTCR, current noise, ESD characteristics, and STOL may be added in arange in which the effect of the present invention is not impaired.Examples of the additives include Nb₂O₅, Ta₂O₅, TiO₂, CuO, MnO₂, ZnO,ZrO₂, La₂O₃, Al₂O₃, V₂O₅, and glass (hereinafter referred to as additiveglass, the “additive glass” is a glass component different from thefirst glass component and the second glass component). By blending suchadditives, a resistor having better characteristics throughout a wideresistance value range can be produced. The amount of the additives tobe added is adjusted, as appropriate, according to the purpose of theuse and, for example in the case of a metal oxide-based additive such asNb₂O₅, the amount is generally about 0.1 to about 10 parts by massrelative to 100 parts by mass of a total inorganic solid content in aresistive composition. In the case of adding the additive glass, morethan 10 parts by mass of the additive glass is added in some cases.

[Organic Vehicle]

In the present invention, by mixing the ruthenium-based conductiveparticles and glass frit with an organic vehicle together with thefunctional filler and/or additives blended if necessary, a resistivecomposition in a form of paste, paint, or ink, having rheology suitablefor a method to which the resistive composition is applied, such asscreen printing, is formed.

The organic vehicle is not limited to particular organic vehicles andthe vehicle generally used in resistive compositions may be used,examples of which include solvents such as terpineol (hereinafterreferred to as TPO), carbitol, butyl carbitol, cellosolve,butylcellosolve, esters thereof, toluene, and xylene; and a solutionobtained by dissolving a resin such as ethylcellulose, nitrocellulose,acrylic acid ester, methacrylic acid ester, or rosin in the solvent. Aplasticizer, a viscosity modifier, a surfactant, an oxidant, a metalorganic compound, and the like may also be added if necessary.

The amount of the organic vehicle to be blended may be in a rangegenerally blended in a resistive composition and can be adjusted, asappropriate, according to an application method such as printing forforming a resistor. 50 to 80 percent by mass of inorganic solid and 50to 20 percent by mass of organic vehicle are preferable.

[Resistive Composition]

The resistive composition in the present invention is produced by mixingand kneading the ruthenium-based conductive particles and glass frit,and the functional filler and/or an additive to be added if necessary,with an organic vehicle and uniformly dispersing them in accordance witha usual method. The composition in the present invention is not limitedto be in a form of paste and the composition may also be in a form ofpaint or ink.

[Production of Resistor]

According to an ordinary procedure, the resistive composition in thepresent invention is printed/applied by a printing method or the like ina predetermined pattern onto an object to be printed, such as aninsulating substrate such as an alumina substrate or a glass ceramicssubstrate or a laminate electronic component, dried, and then fired at ahigh temperature of, for example, about 600° C. to 900° C. A protectivefilm is generally formed on the thick film resistor thus formed bybaking an overcoat glass, and the resistance value is adjusted by lasertrimming or the like if necessary.

As a distribution form of the resistive composition as a product, acombination of two or more kinds of resistive compositions that formresistors having different resistance values is sold and distributed asa set in many cases.

The resistive composition of the present invention is suitable for this,and by providing two or more kinds of resistive compositions of thepresent invention as a set, a resistive composition that can form aresistor having a desired resistance value, by blending a plurality ofthe resistive compositions, as appropriate, by a user can be prepared.Accordingly, a wide resistance range can be covered by the plurality ofresistive compositions having similar compositions.

EXAMPLES

The present invention is described in further detail below withreference to the examples. The present invention, however, is notlimited by these examples.

The physical properties of samples prepared in the examples weremeasured by the following measurement devices and measurement methods.

[Rs (Sheet Resistance)]

The sheet resistance was measured using a digital multimeter “3458A”manufactured by Agilent Technologies, Inc. and was converted to thevalue of a fired film thickness of 8 μm. 20 samples were subjected tothe measurement, and an average thereof was calculated.

[TCR]

TCR between +25° and +125° C. (H-TCR) and TCR between −55 and +25° C.(C-TCR) were measured using the digital multimeter. 20 samples weresubjected to the measurements, and averages thereof were calculated.

[Tg, Tg′, TMA]

A thermomechanical analyzer “TMA4000S” manufactured by Bruker AXS K.K.was used. 20 samples were subjected to the measurement, and an averagethereof was calculated.

[STOL]

The resistance value change rate after applying 2.5 times of ¼ W ratedvoltage (the maximum of 400 V) for 5 seconds was measured. 20 sampleswere subjected to the measurement, and an average thereof wascalculated.

[Average Particle Size D₅₀]

A laser diffraction/scattering type particle size distribution analyzer“LA950V2” manufactured by HORIBA, Ltd. was used. 20 samples weresubjected to the measurement, and an average thereof was calculated.

<Preliminary Experiment A>

Firstly, experiments for obtaining a glass frit in which, in the casewhere a fired product of a mixture of the glass frit and rutheniumdioxide has a value in a range of 1 kΩ/□ to 1 MΩ/□, the fired productexhibits a temperature coefficient of resistance in a plus range wereperformed.

Experimental Examples 1 to 42

Glass frits each having the glass composition as shown in Table 1 andhaving an average particle size D₅₀ of 2 μm were produced and used assamples 1 to 42.

Subsequently, ruthenium dioxide (manufactured by Shoei Chemical Inc.,product name: Ru-109, an average particle size D₅₀=0.05 μm) providedseparately from the samples and each of the samples 1 to 42 were mixedso as to have a mass ratio of 20:80. Thereafter, a composition obtainedby adding 30 parts by mass of an organic vehicle to 100 parts by mass ofeach of the mixtures was kneaded with three rolls. Thus, pastes ofexperimental examples 1 to 42 corresponding to the samples 1 to 42respectively were produced. As the organic vehicle, an organic vehicleobtained by mixing 15 parts by mass of ethylcellulose and TPO as asolvent at an amount of the balance was used.

A 1 mm×1 mm pattern was printed on an alumina substrate onto whichsilver thick film electrodes had been baked in advance, using eachpaste, then subjected to leveling at room temperature for 10 minutes,dried at 150° C. for 10 minutes, and thereafter fired at 850° C. (peaktemperature) for 60 minutes in the atmosphere. Thus, fired patterns ofexperimental examples 1 to 42 corresponding to the samples 1 to 42 wereobtained.

The resistance values Rs of the fired patterns were measured, and theTCR between +25° C. and +125° C. (hereinafter referred to as H-TCR) andthe TCR between −55° C. and +25° C. (hereinafter referred to as C-TCR)of the fired patterns having resistance values of about 1 kΩ/□ and 1kΩ/□ or more were measured.

The measurement results are shown in Table 1.

In Table 1, as to the samples having Rs of less than 1 kΩ/□, themeasurements of the H-TCR and the C-TCR were omitted, and the sign “−”is indicated in the table.

As to the samples 11, 13, 30, 38, 39, and 41 used in the experimentalexamples 11, 13, 30, 38, 39, and 41 in which the H-TCR and the C-TCRwere in the plus ranges among the experimental examples 1 to 42, pasteseach having a mass ratio of ruthenium dioxide and each sample of 10:90were produced in the same manner as mentioned above, and fired patternswere obtained.

Thereafter, in the same manner as mentioned above, the resistance valuesRs of the respective patterns were measured, and the H-TCR and the C-TCRof the patterns except for patterns whose resistance values could not bemeasured, were measured. The results are shown in Table 1.

TABLE 1 Glass Experimental frit example Sample Composition [mol %] No.No. SiO₂ PbO B₂O₃ Al₂O₃ CaO ZnO MgO BaO Na₂O K₂O Li₂O ExperimentalSample 1 3.4 12.9 24.5 — — 59.2 — — — — — example 1 Experimental Sample2 3.4 4.0 — 0.3 — 92.4 — — — — — example 2 Experimental Sample 3 8.711.6 23.3 0.5 — 55.2 — 0.7 — — — example 3 Experimental Sample 4 9.2 —25.6 8.6  1.4 53.2 — 2.0 — — — example 4 Experimental Sample 5 10.4 —31.5 2.2 — 55.8 — — — — — example 5 Experimental Sample 6 10.9 — 24.30.1 — 57.7 7.0 — — — — example 6 Experimental Sample 7 11.5 2.9 26.0 — —59.5 — 0.2 — — — example 7 Experimental Sample 8 22.0 — 29.3 3.2 — 25.3— 3.6 16.6  — — example 8 Experimental Sample 9 36.7 24.0 34.8 2.2 — — —— 0.8 1.6 — example 9 Experimental Sample 37.6 37.7 11.9 1.1 —  6.2 — —5.5 — — example 10 10 Experimental Sample 39.4 8.0 22.7 7.4  9.9 — 3.29.0 0.5 — — example 11 11 Experimental Sample 40.2 30.4 8.6 0.7 —  7.8 —— 5.8 6.5 — example 12 12 Experimental Sample 43.6 — 27.9 — — — — 28.5 — — — example 13 13 Experimental Sample 47.3 — 35.4 7.5 — — — 9.5 0.2 —— example 14 14 Experimental Sample 49.0 15.2 7.3 6.4 15.9  5.8 0.4 — —— — example 15 15 Experimental Sample 49.1 49.1 — 0.5  0.6 — 0.1 — 0.30.2 — example 16 16 Experimental Sample 51.9 33.1 14.6 0.3 — — — — — — —example 17 17 Experimental Sample 53.2 25.8 14.9 4.7 — — — — — 1.5 —example 18 18 Experimental Sample 54.2 17.4 9.9 8.0 —  7.6 — 0.5 — 2.4 —example 19 19 Experimental Sample 55.2 15.6 11.5 1.9 15.5 — 0.2 — 0.20.1 — example 20 20 Experimental Sample 55.3 — — 6.2  1.9 16.1 — 20.5  —— — example 21 21 Experimental Sample 56.1 — 20.3 1.8 10.2  2.8 — — 7.51.3 — example 22 22 Experimental Sample 56.5 — 6.4 4.0  6.3 15.2  —11.6  — — — example 23 23 Experimental Sample 57.5 9.1 12.4 7.5 10.2 — —— 3.3 — — Example 24 24 Experimental Sample 57.7 18.5 11.9 2.7  0.3  5.1— — 1.7 2.2 — example 25 25 Experimental Sample 58.0 21.2 13.5 2.9 — 3.0 — — — 1.4 — example 26 26 Experimental Sample 58.6 5.0 2.5 4.6 15.7— — 9.9 2.6 1.0 — example 27 27 Experimental Sample 58.7 8.1 0.1 4.7 9.5  1.1 — 13.6  2.9 1.2 — example 28 28 Experimental Sample 59.1 9.91.8 6.8 19.7  2.2 0.4 — — — — example 29 29 Experimental Sample 59.8 0.2— 5.0 18.3  2.6 0.2 — 9.4 4.5 — example 30 30 Experimental Sample 60.20.1 14.5 3.0  5.6  3.7 — 1.4 9.2 2.3 — example 31 31 Experimental Sample61.4 20.9 14.2 3.4 — — — — — — — example 32 32 Experimental Sample 62.734.3 1.5 0.6 — — — — 0.8 0.1 — example 33 33 Experimental Sample 63.07.1 10.1 7.3 10.5  1.8 0.2 — — — — example 34 34 Experimental Sample63.7 15.9 16.6 3.8 — — — — — — — example 35 35 Experimental Sample 64.429.2 — 3.9 —  0.1 — — 1.3 1.2 — example 36 36 Experimental Sample 71.80.3 — 3.7  0.2  3.4 4.7 — 15.6  0.3 — example 37 37 Experimental Sample74.2 — — 2.0 — — — 5.2 0.4 18.3  — example 38 38 Experimental Sample76.2 — — 2.0 — — — 4.6 7.0 4.9 5.3 example 39 39 Experimental Sample80.9 — — 2.1 — — — 4.8 7.1 5.1 — example 40 40 Experimental Sample 82.3— 16.0 0.1 — — 0.2 — — 1.4 — example 41 41 Experimental Sample 84.8 — —2.6 — — — 4.3 8.3 — — example 42 42 Ru-based particles/Glass fritRu-based particles/Glass frit (mass ratio) = (mass ratio) = Experimental20/80 10/90 example Rs H-TCR C-TCR Rs H-TCR C-TCR No. (Ω/□) (ppm/° C.)(ppm/° C.) (Ω/□) (ppm/° C.) (ppm/° C.) Experimental 0.465k — — — — —example 1 Experimental 20.9k −162 −155 — — — example 2 Experimental0.827k — — — — — example 3 Experimental 28.0k  −43  −33 — — — example 4Experimental 40.2k −445 −460 — — — example 5 Experimental 9.78k −195−199 — — — example 6 Experimental 1.49k  −48  −49 — — — example 7Experimental 0.709k — — — — — example 8 Experimental 0.211M  −95 −166 —— — example 9 Experimental 90.4k −177 −218 — — — example 10 Experimental1.17k  280  269 0.187M −77 −73 example 11 Experimental 0.215k — — — — —example 12 Experimental 7.66k  165  147 0.877M  73  70 example 13Experimental 8.87k  −47  −42 — — — example 14 Experimental 89.3k −144−201 — — — example 15 Experimental 0.248M −134 −223 — — — example 16Experimental 0.789M −172 −228 — — — example 17 Experimental 0.713M −198−278 — — — example 18 Experimental 0.146M −278 −347 — — — example 19Experimental 0.332M  −95 −201 — — — example 20 Experimental 0.331k — — —— — example 21 Experimental 9.03k  −20  −59 — — — example 22Experimental 21.4k   9  −7 — — — example 23 Experimental 55.7k  −82 −145— — — Example 24 Experimental 0.298M −199 −286 — — — example 25Experimental 45.7k −139 −219 — — — example 26 Experimental 0.474k — — —— — example 27 Experimental 0.866k — — — — — example 28 Experimental0.181M −143 −177 — — — example 29 Experimental 6.84k  158  115 ∞ — —example 30 Experimental 13.9k −178 −225 — — — example 31 Experimental0.148M −245 −301 — — — example 32 Experimental 0.362M −253 −347 — — —example 33 Experimental 0.372M −231 −287 — — — example 34 Experimental0.252M −199 −243 — — — example 35 Experimental 0.360M −218 −309 — — —example 36 Experimental 0.653k — — — — — example 37 Experimental 26.7k 305  371 ∞ — — example 38 Experimental 20.3k  221  200 ∞ — — example 39Experimental 3.14M  22  −31 — — — example 40 Experimental 50.4k  415 655 ∞ — — example 41 Experimental 0.255M −524 −545 — — — example 42

As shown in Table 1, in the preliminary experiment A, only the sample 13among the samples 1 to 42 showed that all of TCRs were in the plusrange.

In order to analyze in further detail, glass frits having compositionscontaining, as main components, SiO₂, B₂O₃, and BaO as in the sample 13(samples 43 to 50 in Table 2) were newly provided, and pastes havingmass ratios of ruthenium dioxide and each glass frit of 30:70, 20:80,and 10:90 were produced. Subsequently, a fired pattern was obtainedusing each paste, and the glass transition point Tg and coefficient ofthermal expansion a, and the resistance value Rs, H-TCR, and C-TCR ofthe fired pattern were measured.

Furthermore, in order to evaluate the denseness of the surface of thefired film, the fired surface of each pattern was observed by visualcheck, and the pattern in which unevenness (convexconcave) was clearlyobserved on the surface was indicated by “x”, and the patterns in whichunevenness was slightly observed were indicated by “Δ”, and the patternsin which unevenness was hardly observed were indicated by “◯”.

The results are shown in Table 2.

TABLE 2 Glass Ru-based particles/Glass frit (mass ratio) Experimentalfrit Glass composition 30/70 20/80 example Sample [mol %] Rs H-TCR C-TCRRs H-TCR C-TCR No. No. SiO₂ B₂O₃ BaO (Ω/□) (ppm/° C.) (ppm/° C.) (Ω/□)(ppm/° C.) (ppm/° C.) Experimental Sample 43.6 27.9 28.5 0.953k 260 1437.66k 165 147 example 13 13 Experimental Sample 30.0 30.0 40.0 18.2k 12691 0.442M 109 59 example 43 43 Experimental Sample 30.0 35.0 35.0 3.96k201 192 95.6k 75 46 example 44 44 Experimental Sample 30.0 40.0 30.01.73k 215 188 25.3k 67 31 example 45 45 Experimental Sample 41.0 26.033.0 11.9k 150 131 0.447M 112 82 example 46 46 Experimental Sample 45.031.0 24.0 1.02k 232 221 21.0k 57 33 example 47 47 Experimental Sample50.0 15.0 30.0 0.530k 349 339 5.62k −130 100 example 48 48 ExperimentalSample 50.0 25.0 25.0 0.678k 375 353 18.0k 129 109 example 49 49Experimental Sample 50.0 35.0 15.0 0.664k1 235 223 10.4k 22 −28 example50 50 Ru-based particles/Glass frit Coefficient (mass ratio) ofDenseness Experimental 10/90 thermal of example Rs H-TCR C-TCR Tgexpansion α fired No. (Ω/□) (ppm/° C.) (ppm/° C.) (° C.) (×10⁻⁷/° C.)surface Experimental 1.02M 73 70 629.7 82.3 ◯ example 13 Experimental12.5M 216 152 603.0 94.0 Δ example 43 Experimental 5.53M 122 84 620.585.5 Δ example 44 Experimental 2.72M 48 4 625.5 76.6 Δ example 45Experimental 10.5M 191 155 620.5 91.8 ◯ example 46 Experimental 2.10M 587 631.0 71.4 ◯ example 47 Experimental 15.7M −840 −866 654.0 93.2 Xexample 48 Experimental 12.2M 82 44 661.0 73.1 ◯ example 49 Experimental2.22M −41 −89 628.0 62.2 Δ example 50

As can be seen from the results shown in Table 2, it can be said thatthe glass frits of the samples 13, 43, 44, 45, 46, 47, and 49 used inthe experimental examples 13, 43, 44, 45, 46, 47, and 49 are glass fritswhich each provide a fired product of the mixture of the glass frit andthe ruthenium dioxide showing a temperature coefficients of resistancein a plus range when the fired product has a value in a range of 1 kΩ/□to 1 MΩ/□.

The examples described below show examples of producing resistors fromresistive compositions that contain the glass frit of the sample 13.

<Preliminary Experiment B>

Subsequently, preliminary experiments for a functional filler forimproving characteristics such as withstand voltage characteristics,electrostatic characteristics, a change in resistance value wereperformed.

As a glass having a low fluidity at the time of firing, glass particles(average particle size D₅₀=2 μm, Tg′=713° C.) containing, in terms ofoxide, 76.4 mol % of SiO₂, 3.3 mol % of B₂O₃, 6.5 mol % of Al₂O₃, 11.1mol % of CaO, 1.2 mol % of MgO, 0.3 mol % of La₂O₃, 1.1 mol % of K₂O,and 0.1 mol % of ZrO₂ were provided.

Ruthenium dioxide (Ru-109) was provided as conducting particlescontained in a filler, and the above glass particles and the conductingparticles were mixed so that the contents of the conducting particles inthe filler were 20 percent by mass, 30 percent by mass, and 40 percentby mass, each of the mixtures was stirred with a ball mill using a mediahaving a diameter of 5 mm and alcohol as a solvent, and thereafter, themixture was subjected to a thermal treatment at 880° C. The mixture wasagain pulverized with the above-mentioned ball mill so that the averageparticle size D₅₀ of the filler became 3 μm, and three kinds of fillerswere produced.

When each resultant filler was observed with a scanning electronmicroscope (SEM), a structure in which particles of ruthenium dioxidehaving a relatively small particle size (0.05 μm) were adhered/dispersedon the surfaces of the glass particles having a relatively largeparticle size (about 3 μm) and inside the glass particles in thevicinity of the surfaces was observed.

Each of these fillers and the glass frit of the sample 13 were mixed soas to have mass ratios of 50:50, 40:60, and 30:70, and fired patternswere produced in the same manner as in the preliminary experiment A.

Furthermore, each of these fillers, ruthenium dioxide (Ru-109), and theglass frit of the sample 13 were mixed so as to have mass ratios of45:5:50, 35:5:60, and 25:5:70, and fired patterns were produced in thesame manner as mentioned above.

The resistance values Rs and STOL of each of these patterns weremeasured. The results are shown in Table 3.

In Table 3, as to the patterns in which it was difficult to performmeasurements of STOL because the resistance values were high andunstable, the measurements were omitted, and the sign “−” is shown inTable 3.

TABLE 3 Filler/Ru-based particles/ Filler/Glass frit Glass frit (massratio) (mass ratio) 50/50 40/60 30/70 45/5/50 35/5/60 25/5/70 Content ofRu-based 20 Rs (Ω/□) ∞ ∞ ∞ 18.9M 27.3M 33.0M particles in filler STOL(%) — — — — — — (precent by mass) 30 Rs (Ω/□) 5.28M 51.5M ∞ 574k 1.30M2.91M STOL (%) −0.91 0.28 — −0.59 −0.27 −0.33 40 Rs (Ω/□) 274k 1.19M5.58M 89.5k 411k 1.07M STOL (%) −2.19 −0.59 −0.09 −3.19 −0.64 −0.23

As shown in Table 3, when the content of the conducting particles in thefiller was 20 percent by mass, the conduction was not obtained by onlyusing the filler, and the conduction was obtained by adding a smallamount of ruthenium dioxide. On the other hand, when the content was 40percent by mass, the STOL became excessively large and thus such acontent was not suitable for practical use.

The above-described results demonstrate that, in the present invention,the content of the conducting particles in the filler is preferably inthe range of 20 to 35 percent by mass.

Example 1

The present example is an example in the case of containing a functionalfiller as a component of a resistive composition.

Examples 1-1 to 1-6

Compositions obtained by blending ruthenium dioxide (Ru-109), the fillerhaving a content of conducting particles of 30 percent by mass, producedin the preliminary experiment B, and a glass frit of the sample 13,produced in the preliminary experiment A, in amounts of the parts bymass shown in Table 4 and adding 30 parts by mass of an organic vehiclewere kneaded with three rolls. Thus, pastes of Examples 1-1 to 1-6 wereproduced. As the organic vehicle, an organic vehicle obtained by mixing15 parts by mass of ethylcellulose and the balance of TPO was used.

A 1 mm×1 mm pattern was printed on an alumina substrate onto whichsilver thick film electrodes had been baked in advance, using eachpaste, then subjected to leveling at room temperature for 10 minutes,dried at 150° C. for 10 minutes, and thereafter fired at 850° C. (peaktemperature) for 60 minutes in the atmosphere. Thus, resistors wereobtained.

The sheet resistance value Rs, H-TCR, C-TCR, variation CV in resistancevalue, noise, and STOL of each resistor were measured. The CV wasdetermined from the values measured for 20 resistors.

The measurements results are shown in Table 4.

In Table 4, as to the resistors, the noise of which was difficult tomeasure because of overrange, the measurement was omitted, and the sign“−” is shown in Table 4.

Moreover, the resistance value Rs set as a target value for each pasteis also shown in Table 4 as a reference.

TABLE 4 Example 1-1 1-2 1-3 1-4 1-5 1-6 Target Rs (Ω/□) 100   1k   10k100k   1M   10M Composition ratio (parts by mass) Ru-based particles50.0 28.5 16.5 10.5 6.0 3.0 Filler 0.0 20.5 24.5 26.5 28.0 29.0 Glassfrit 50.0 51.0 59.0 63.0 66.0 68.0 Measured Rs (Ω/□) 99.3 1.08k 10.5k107k 1.09M 9.87M H-TCR (ppm/° C.) 8 −6 13 −9 35 56 C-TCR (ppm/° C.) −20−2 11 −25 7 27 CV (%) 3.4 2.4 1.8 2.4 2.8 7.1 Noise (dB) −25 −19 −11 −2+9 — STOL (%) 0 0 −0.07 −0.27 −0.12 −0.02

As can be seen from Table 4, according to the present invention,resistors having superior current noise characteristics and loadcharacteristics in a whole wide resistance range (100 Ω/□ to 10 MΩ/□)could be obtained, and especially, a TCR within ±100 ppm/° C. could beachieved.

Furthermore, the results of analysis of the resultant resistor byScanning Electron Microscope/Energy Dispersive X-ray Spectrometry(SEM-EDX) is shown in FIG. 1A to FIG. 1C. FIG. 1A is an SEM image of theresistor. FIG. 1B is a drawing showing a result of mapping with respectto Ba element, and FIG. 1C is a drawing showing a result of mappingimage with respect to Ru element.

As shown in FIG. 1B, in the resistor obtained in Example 1, a pluralityof discontinuous parts (hereinafter referred to as islands) containingno Ba are scattered in a continuous region (hereinafter referred to as amatrix) containing Ba, and a so-called sea-island structure was found.The glass frit used in this Example 1 contained Ba, whereas the glassparticles used as a filler contained no Ba. Therefore, it is assumedthat, in the resistor of the present invention, the glass particleshaving low fluidity at the time of firing remain in the matrix of theglass frit so as to form islands, and thus, such a sea-island structurewas formed. Moreover, as shown in FIG. 1C, the presence of Ru on thesurfaces of the glass particles at a high concentration was found.Therefore, it is assumed that RuO₂ particles are not uniformly dispersedin the resistor obtained from the resistive composition of the presentinvention, and at least a part of the resistor has a soap foam-likenon-uniform network structure.

Example 2

The present example is an example in the case where a resistivecomposition contains no functional filler.

Examples 2-1 to 2-6

As a glass frit having a composition close to the sample 13, sample 51(in terms of oxide, 38.1 mol % of SiO₂, 26.1 mol % of B₂O₃, 27.2 mol %of BaO, 0.8 mol % of Al₂O₃, 0.5 mol % of SrO, 3.6 mol % of ZnO, 3.2 mol% of Na₂O, and 0.5 mol % of K₂O) was newly provided. The Tg of thesample 51 was 629.4° C.

Additive glass was added to the paste for the purpose of adjusting theTCR. As the additive glass, an additive glass (in terms of oxide, 43.0mol % of SiO₂, 18.2 mol % of B₂O₃, 13.0 mol % of Al₂O₃, 2.8 mol % ofCaO, 3.2 mol % of MgO, 1.3 mol % of SnO₂, 1.9 mol % of Co₂O₃, 6.6 mol %of K₂O, and 10.0 mol % of Li₂O) was provided. The glass transition pointof the additive glass was 494.0° C.

Compositions obtained by blending ruthenium dioxide (Ru-109), theadditive glass, and the glass frit of the sample 51 in amounts of theparts by mass shown in Table 5 and adding 30 parts by mass of an organicvehicle and the parts by mass of the other additives shown in Table 5were kneaded with three rolls. Thus, pastes were produced. As theorganic vehicle, an organic vehicle obtained by mixing 15 parts by massof ethylcellulose and the balance of TPO was used.

A 1 mm×1 mm pattern was printed on an alumina substrate onto whichsilver thick film electrodes had been baked in advance, using eachpaste, then subjected to leveling at room temperature for 10 minutes,dried at 150° C. for 10 minutes, and thereafter fired at 850° C. (peaktemperature) for 60 minutes in the atmosphere. Thus, resistors wereobtained.

The sheet resistance value Rs, H-TCR, C-TCR, variation CV in resistancevalue, and noise of each resistor were measured.

The measurement results are shown in Table 5.

TABLE 5 Example 2-1 2-2 2-3 2-4 2-5 2-6 Target Rs (Ω/□) 100   1k   10k 100k   1M   10M Composition ratio (parts by mass) Ru-based 50.0 33.322.5 17.1 11.7 10.4 particles Additive glass 40.0 28.0 20.0 16.0 12.011.0 Glass frit 10.0 38.7 57.5 66.9 76.3 78.6 Other additives (outeraddition) MnO₂ 0.60 Nb₂O₅ 0.13 0.18 0.10 0.06 0.02 0.01 Ta₂O₅ 0.50 0.500.50 0.50 0.50 CuO 0.20 0.30 0.40 0.40 Measured Rs (Ω/□) 93.4 1.09k9.07k 99.0k 1.09M 9.00M H-TCR (ppm/° C.) 8 −22 17 −18 4 15 C-TCR (ppm/°C.) −30 −28 16 −33 −17 −19 CV (%) 6.69 5.24 0.85 4.71 4.07 10.29 Noise(dB) −27 −21 −11 −5 11 —

As can be seen from Table 5, the present invention could cause the TCRwithin 100 ppm/° C. in a wide resistance range even in the case ofcontaining no functional filler.

Example 3

The same experiments as in the preliminary experiments A and B andExamples 1 and 2 were performed except that the ruthenium-basedconductive particles to be used were changed to each of rutheniumdioxide (manufactured by Shoei Chemical Inc., Product name: Ru-108)having an average particle size D₅₀=0.20 μm and ruthenium dioxide(manufactured by Shoei Chemical Inc., Product name: Ru-105) havingD₅₀=0.02 μm. Almost the same results were obtained.

1. A thick film resistor comprising a fired product of a resistivecomposition, wherein the thick film resistor comprises ruthenium-basedconductive particles containing ruthenium dioxide and a glass componentbeing essentially free of a lead component; the glass component containsat least a first glass component and a second glass component having aglass transition point that is higher than the first glass component;and the thick film resistor has a sea-island structure in which thesecond glass component is scattered in a matrix of the first glasscomponent so as to form islands, and has a resistance value in a rangeof 100 Ω/□ to 10 MΩ/□ and a temperature coefficient of resistance within±100 ppm/° C.
 2. The thick film resistor according to claim 1, whereinthe thick film resistor has a resistance value in a range of 1 kΩ/□ to10 MΩ/□.
 3. The thick film resistor according to claim 2, wherein thethick film resistor has a resistance value in a range of 10 kΩ/□ to 10MΩ/□.
 4. The thick film resistor according to claim 3, wherein the thickfilm resistor has a resistance value in a range of 100 kΩ/□ to 10 MΩ/□.5. The thick film resistor according to claim 4, wherein the thick filmresistor has a resistance value in a range of 1 MΩ/□ to 10 MΩ/□.
 6. Thethick film resistor according to claim 1, wherein the first glasscomponent comprises a glass component derived from a glass frit which isconstituted such that in the case where a fired product of a mixture ofthe glass frit and the ruthenium dioxide has a value in a range of 1kΩ/□ to 1 MΩ/□, the fired product exhibits a temperature coefficient ofresistance in a plus range.
 7. The thick film resistor according toclaim 6, wherein the glass frit comprises, in terms of oxide, 20 to 45mol % of BaO, 20 to 45 mol % of B₂O₃, and 25 to 55 mol % of SiO₂. 8.(canceled)
 9. The thick film resistor according to claim 1, wherein thethick film resistor has a structure in which a part of the rutheniumdioxide is present at a high concentration on a surface of the secondglass component that is scattered so as to form islands and the vicinityof the surface.
 10. The thick film resistor according to claim 1,wherein the ruthenium-based conductive particles have an averageparticle size D₅₀ of 0.01 to 0.2 μm.
 11. (canceled)
 12. (canceled) 13.The method for producing a thick film resistor according to claim 22,wherein the glass frit comprises, in terms of oxide, 20 to 45 mol % ofBaO, 20 to 45 mol % of B₂O₃, and 25 to 55 mol % of SiO₂.
 14. The methodfor producing a thick film resistor according to claim 22, wherein theruthenium-based conductive particles have an average particle size D₅₀of 0.01 to 0.2 μm.
 15. (canceled)
 16. The method for producing a thickfilm resistor according to claim 23, wherein the glass particles have aglass transition point Tg′ satisfying a relationship of Tg<Tg′ withrespect to a glass transition point Tg of the glass frit.
 17. The methodfor producing a thick film resistor according to claim 16, wherein theTg is in a range of 450° C. to 700° C. and the Tg′ is 500° C. or more.18. The method for producing a thick film resistor according to claim23, wherein the functional filler contains the conducting particles inan amount of 20 to 35 percent by mass.
 19. The method for producing athick film resistor according to claim 23, wherein the conductingparticles are ruthenium-based conducting particles containing rutheniumdioxide.
 20. The method for producing a thick film resistor according toclaim 23, wherein the conducting particles have an average particle sizeD₅₀ of 0.01 to 0.2 μm.
 21. The method for producing a thick filmresistor according to claim 23, wherein the functional filler has anaverage particle size D₅₀ of 0.5 to 5 μm.
 22. A method for producing athick film resistor having a resistance value in a range of 100 Ω/□ to10 Ω/□, the method comprising: printing a resistive compositioncomprising ruthenium-based conductive particles that contain rutheniumdioxide, a glass frit that is essentially free of a lead component andis constituted such that in a case where a fired product of a mixture ofthe glass frit and the ruthenium dioxide has a value in a range of 1kΩ/□ to 1 MΩ/□, the fired product exhibits a temperature coefficient ofresistance in a plus range, and an organic vehicle, on an object to beprinted, wherein as the resistive composition, two or more resistivecompositions having different contents of the ruthenium-based conductiveparticles and different contents of the glass frit are used and theblending ratio of each of the two or more resistive compositions isadjusted; and thereafter firing the resistive composition at 600° C. to900° C.
 23. A method for producing a thick film resistor, the methodcomprising: printing a resistive composition comprising ruthenium-basedconductive particles that contain ruthenium dioxide, a glass frit thatis essentially free of a lead component and is constituted such that ina case where a fired product of a mixture of the glass frit and theruthenium dioxide has a value in a range of 1 kΩ/□ to 1 MΩ/□, the firedproduct exhibits a temperature coefficient of resistance in a plusrange, a functional filler that is composite particles comprising glassparticles which are essentially free of a lead component and conductingparticles which have a smaller particle size than the glass particlesand are essentially free of a lead component, and an organic vehicle, onan object to be printed; and thereafter firing the resistive compositionat 600° C. to 900° C.
 24. The method for producing a thick film resistoraccording to claim 23, wherein the glass frit comprises, in terms ofoxide, 20 to 45 mol % of BaO, 20 to 45 mol % of B₂O₃, and 25 to 55 mol %of SiO₂.
 25. The method for producing a thick film resistor according toclaim 23, wherein the ruthenium-based conductive particles have anaverage particle size D₅₀ of 0.01 to 0.2 μm.